How to access GPIO in LS1021AIOT board from u-boot.

I have used few processor pins as GPIO and I want to add specific GPIO functionality(set , clear , toggle) to those pin. Which files to include for GPIO support for LS1021AIOT board. I didn't find a files that I can use and modify GPIO at will . Can nay one guide me here ?? I do know the set and clear function for u-boot. but I am talking about the structure for GPIO.

We do not offer GPIO driver for U-boot for our LS1021A processor, but U-boot driver structure is relatively simple, so you can create your own GPIO driver using other GPIO drivers as reference. For example drivers please look /drivers/gpio/ folder in U-boot sources.

Thanks . Is it possible to only use part of a PORT pins as GPIO ??? For Example I have eMMC connected on my BOARD which uses pins multiplexed with GPIO4 and I want to use GPIO4_21 and GPIO4_22 as GPIO pins for ls1020a .